arm and axilla

What is the axilla?

A pyramidal-shaped region between the neck and upper limb that serves as a passageway for neurovascular structures entering and leaving the upper limb.

What are the four walls of the axilla?

Anterior, posterior, medial, and lateral walls.

What forms the anterior wall of the axilla?

Pectoralis major, pectoralis minor, subclavius, and clavipectoral fascia.

What forms the medial wall of the axilla?

Upper thoracic wall (ribs and intercostal muscles) and serratus anterior.

What forms the lateral wall of the axilla?

Intertubercular sulcus (bicipital groove) of the humerus.

What forms the posterior wall of the axilla?

Costal surface of scapula, subscapularis, latissimus dorsi, and teres major; long head of triceps contributes to the posterior boundary.

What are the boundaries of the axillary inlet (apex)?

Medially: lateral border of first rib. Anteriorly: clavicle. Posteriorly: superior border of scapula.

What structures pass through the axillary inlet?

Axillary artery, axillary vein, and inferior trunk of brachial plexus.

Where does the subclavian artery become the axillary artery?

At the lateral border of the first rib.

Where does the axillary artery become the brachial artery?

At the inferior border of teres major.

What are the contents of the axilla?

Axillary artery and vein, brachial plexus, lymph nodes and vessels, biceps brachii and coracobrachialis, and axillary process of the breast.

What are the three posterior axillary spaces?

Quadrangular space, triangular space, and triangular interval.

What are the boundaries and contents of the quadrangular space?

Boundaries: Teres minor superiorly, teres major inferiorly, long head of triceps medially, and surgical neck of humerus laterally. Contents: Axillary nerve and posterior circumflex humeral artery and vein.

What are the boundaries and contents of the triangular space?

Boundaries: Teres minor superiorly, teres major inferiorly, and long head of triceps laterally. Contents: Circumflex scapular artery and vein.

What are the boundaries and contents of the triangular interval?

Boundaries: Teres major superiorly, long head of triceps medially, and humeral shaft/lateral head of triceps laterally. Contents: Radial nerve and profunda brachii artery.

Which nerve and artery travel together through the quadrangular space?

Axillary nerve and posterior circumflex humeral artery.

Which nerve and artery travel together through the triangular interval?

Radial nerve and profunda brachii artery.

What is the clinical significance of the quadrangular space?

Compression or injury can affect the axillary nerve, causing deltoid and teres minor weakness and sensory loss over the lateral shoulder.

What is the axillary process (tail of Spence)?

Superolateral extension of mammary gland tissue along the inferior margin of pectoralis major toward the axilla.

How many groups of axillary lymph nodes are described in the lecture?

Five groups: humeral (lateral), pectoral (anterior), subscapular (posterior), central, and apical.

Which lymph nodes primarily drain the upper limb?

Humeral (lateral) axillary lymph nodes.

Which axillary lymph nodes receive drainage from the mammary gland?

Pectoral (anterior) nodes; approximately 75% of breast lymph drainage is directed toward axillary nodes.

Which axillary lymph nodes drain the posterior axillary wall, back, shoulder, and neck?

Subscapular (posterior) nodes.

What is the function of central axillary lymph nodes?

Receive lymph from humeral, pectoral, and subscapular groups.

What is the first part of the axillary artery and its branch?

Pre-pectoral part; gives off the superior thoracic artery.

What are the branches of the second part of the axillary artery?

Thoracoacromial artery and lateral thoracic artery.

What are the four branches of the thoracoacromial artery?

Pectoral, deltoid, acromial, and clavicular branches.

What does the lateral thoracic artery supply?

Pectoral muscles, serratus anterior, intercostal muscles, axillary lymph nodes, and lateral aspect of the breast.

What are the three branches of the third part of the axillary artery?

Subscapular artery, anterior circumflex humeral artery, and posterior circumflex humeral artery.

What is the largest branch of the axillary artery?

Subscapular artery.

What are the terminal branches of the subscapular artery?

Circumflex scapular artery and thoracodorsal artery.

Which artery passes through the triangular space?

Circumflex scapular artery.

Which artery passes through the quadrangular space?

Posterior circumflex humeral artery.

Which artery accompanies the axillary nerve around the surgical neck of the humerus?

Posterior circumflex humeral artery.

What is an axillary artery aneurysm?

Abnormal dilation of the axillary artery, potentially compressing the brachial plexus and producing pain, anesthesia, and muscle weakness.

Which portion of the axillary artery is emphasized in the lecture for aneurysm-related brachial plexus compression?

First part of the axillary artery, where the trunks of the brachial plexus are vulnerable.

What are the boundaries of the axillary vein?

It begins at the lower margin of teres major as a continuation of the basilic vein and ends at the lateral border of the first rib, where it becomes the subclavian vein.

Where does the cephalic vein drain?

Into the axillary vein near its termination.

What are the superficial veins of the arm?

Basilic vein (medial) and cephalic vein (lateral).

What are the deep veins of the arm?

Paired brachial veins, which drain into the basilic or axillary vein.

What are the two compartments of the arm and their main functions?

Anterior compartment: elbow flexion. Posterior compartment: elbow extension.

Which nerve innervates the anterior compartment of the arm?

Musculocutaneous nerve (primarily C5-C7).

Which nerve innervates the posterior compartment of the arm?

Radial nerve (C6-C8).

What are the OINA of biceps brachii?

O: Short head—coracoid process; long head—supraglenoid tubercle of scapula. I: Radial tuberosity. N: Musculocutaneous nerve (C5-C6). A: Powerful elbow flexion and forearm supination; accessory shoulder flexion.

What are the OINA of coracobrachialis?

O: Apex of coracoid process. I: Medial midshaft of humerus. N: Musculocutaneous nerve (C5-C7). A: Flexes and adducts arm at glenohumeral joint.

What are the OINA of brachialis?

O: Distal half of anterior humerus. I: Coronoid process and tuberosity of ulna. N: Musculocutaneous nerve (C5-C6), with radial nerve contribution (C5-C7) according to the lecture. A: Primary elbow flexor in all forearm positions.

What are the OINA of triceps brachii?

O: Long head—infraglenoid tubercle; medial head—posterior humerus below radial groove; lateral head—posterior humerus above radial groove. I: Olecranon of ulna. N: Radial nerve (C6-C8). A: Extends forearm at elbow; long head also extends and adducts arm at shoulder.

What are the OINA of anconeus?

O: Lateral epicondyle of humerus. I: Olecranon and posterior surface of ulna. N: Radial nerve (C6-C8, as listed in the arm lecture). A: Assists elbow extension, stabilizes elbow capsule, and abducts ulna during pronation.

Which nerve pierces coracobrachialis?

Musculocutaneous nerve.

Which major structures pass deep to coracobrachialis?

Median nerve and brachial artery.

What happens in proximal rupture of the long head of biceps brachii?

Tear of its proximal attachment at the supraglenoid tubercle, often associated with chronic tendinitis or forceful resisted arm flexion; produces a Popeye deformity.

What happens in distal biceps tendon rupture?

Tear at the radial tuberosity, often during eccentric loading; produces pain and a pop in the antecubital fossa, with significant impairment of supination and elbow flexion. It does not produce the classic proximal Popeye sign.

What is the function of the profunda brachii artery?

Largest branch of the brachial artery; accompanies the radial nerve in the radial groove and gives middle and radial collateral branches.

What are the terminal branches of the brachial artery?

Radial and ulnar arteries.

What are the superior and inferior ulnar collateral arteries' relationships to the elbow?

Superior ulnar collateral accompanies the ulnar nerve posterior to the medial epicondyle; inferior ulnar collateral passes anterior to the medial epicondyle.

What are the clinical risks of axillary/subclavian venous access?

Pneumothorax, arterial injury, hematoma, pseudoaneurysm, nerve injury, and catheter misplacement.